Numerous such sensor units with which the lighting devices of a motor vehicle are controlled as a function of signals from light-sensitive sensors are known, e.g., from published German Patent Application 199 33 642. They have sensors which detect the lighting conditions outside the vehicle, the sensors being connected to an analyzing device in which it is determined from the sensor signals whether the currently existing lighting conditions make a change in the switching state of the lighting devices necessary. The lighting devices are then switched on or off according to this analysis.